AU603213B2 – Polymer blend for packaging film or sheet
– Google Patents
AU603213B2 – Polymer blend for packaging film or sheet
– Google Patents
Polymer blend for packaging film or sheet
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Publication number
AU603213B2
AU603213B2
AU15686/88A
AU1568688A
AU603213B2
AU 603213 B2
AU603213 B2
AU 603213B2
AU 15686/88 A
AU15686/88 A
AU 15686/88A
AU 1568688 A
AU1568688 A
AU 1568688A
AU 603213 B2
AU603213 B2
AU 603213B2
Authority
AU
Australia
Prior art keywords
weight
percent
blend
polymer
sheet
Prior art date
1987-05-15
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
AU15686/88A
Other versions
AU1568688A
(en
Inventor
Charles C. Hwo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsui Petrochemical Industries Ltd
Shell USA Inc
Original Assignee
Shell Oil Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1987-05-15
Filing date
1988-05-06
Publication date
1990-11-08
1988-05-06
Application filed by Shell Oil Co
filed
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Shell Oil Co
1988-11-17
Publication of AU1568688A
publication
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patent/AU1568688A/en
1990-11-08
Application granted
granted
Critical
1990-11-08
Publication of AU603213B2
publication
Critical
patent/AU603213B2/en
2008-05-06
Anticipated expiration
legal-status
Critical
Status
Ceased
legal-status
Critical
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Classifications
C—CHEMISTRY; METALLURGY
C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
C08L23/18—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms
C08L23/20—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms having four to nine carbon atoms
Abstract
Polymer blends comprising a major preparation of a butene-1 polymer, and minor preparations of an ethylenic polymer and a propylene colymer can be used to provide packaging film or sheet capable of forming peel seals and laminar structures.
Description
To: T1h UUMM1&N1UEt.K UF1′ AENTS (a member of the firm of DAVIES COLLISON for and on behalf of the Applicant).
Davies Collison, Melbourne and Canberra.
COMMONWEALTH OF AUSTRALIA PATENT ACT’ 1-95i COMPLETE SPECI FI!CATION
(ORIGINAL)
FOR OFFICE USE CLASS INT. CLASS Application Number: Lodged: Complete Specif icationi Lodged: Accepted: Published: Priority: Related Art: This document contains the aiT~edments made Under &.-ctjon 49 and is correct for printing.
4 j~i NAME OF APPLICANT: ADDRESS OF APPLICANT: NAME(S) OF INVENTOR(S) ADDRESS FOR SERVICE: SHELL OIL COMPANY AND MITSUI PETROCHEMICAL INDUSTRIES, LTD.
900, Louisiana, Houston, Texas 77001, United States of America, and 3-chome, Kasumigaseki, Chiyoda-ku, Tokyo, Japan, respectively., Charles C. HWO DAVIES COLLISON, Patent Attorneys 1 Little Collins St46reet, Melbourne* 3000.
COMPLETE SPECIFICATION FOR THE INVENTION EMiTITLED: «POLYMER BLEND FOR PACKAGING FILM OR SHEET» The following statement Is a full. decito of this invention.
including the best method of perforaiuig it known to us
-I-
Insert place and date of signature, ucaIlcu at x Signature of Declarant(s) (no Declared at Tokyo this 27th i f .98Q.
Note: Initial all alterations.
DAVIES COLLISON; MELBOURNE and CANBERRA.
-2- The present invention relates to a polymer blend which can be used to provide a heat sealable wrapping or packaging film or sheet (for ease of reference mention will subsequently be made only to film) which is capable of forming a peelable seal. The seal is achievable either between two films of this kind, or between one film of this kind and a polypropylene packing film without the need for an adhesive.
A peelable seal is defined to be the seal between 10 two films produced by heat sealing or impulse sealing, the seal thus formed having the property of being able to open in the original plane of joining of the two films by the action of a pulling force, without wrenching off or tearing occurring in the material of the two films used to make up the seal. For the purposes of the present invention, the peelable seal must possess a mechanical resistance sufficient to maintain the integrity and the tight-seal properties of a packaging or wrapping round an article during storage and transport until such time as the packaging or wrapping is opened by the user of the article. The mechanical resistance of the peelable seal must be low enough to permit ready manual opening of the joint, i.e. without the use of an auxiliary instrument.
Many thermoplastic materials have been employed in the manufacture of films capable of forming peelable seals.
C C! C C i -r-asaxra~ -3- -s-4- For example r-App-licatizn N\4,189,519 discloses a blend for producing a peelable heat seal comprising 50 to percent by weight of a copolymer of 80 to 96 percent by weight ethylene and 4 to 20 percent by weight of an unsaturated ester, and 10 to 50 percent by weight of a crystalline isotactic polybutylene. While capable of forming a peel seal, film of this blend will not bond to polypropylene without an adhesive although it will bond to high density polyethylene (HDPE) without the use of adhesive.
Ls-A- U6 Appli– ation No 3,900,534 discloses thermoplastic shrink films with good heat seal characteristics and good optical properties, but does not address the need for a peel seal film.
Aus -A- 15 Applieatien No\3,817,821 discloses blends of ethylene-vinyl acetate copolymer (EVA) with polybutylene at 20-40 w% but does not include polypropylene in the blend.
U!S- A U.S. Applioati-n N-e3,879,492 discloses blends of polybutylene styrene-butadiene copolymer low density polyethylene (LDPE) high density polyethylene (HDPE) polyisobutylene but does not include polypropylene in the blend.
SS.. Applicabtin No 4,539,263 discloses peel seals based on blends of comonomers and propylene/a-olefin copolymer, but does not provide disclosure directed to polybutylenes.
-4- EPA 213698 discloses blends of an ethylene polymer, a butene-1 polymer and a propylene polymer, the amount of the propylene polymer being less than 15 weight percent of the blend.
There has been a long felt need for wrapping or packaging materials having easy peelability at the seal and yet which will bond to polypropylene without the aid of an adhesive and which are retortable at temperatures of 120°C (250°F) or above.
0. 10 It has now been found that certain properties, including film retortability at 120 0 C (250F) and above, heat seal strength, and peel seal characteristics, of packaging or wrapping films or sheets may be improved by them from blends comprising a major proportion of a butene-1 polymer and minor ,15 proportions of an ethylenic polymer (at most 25w%) and a propylene polymer (at least 25 According to the invention there is therefore provided a polymer blend comprising from 50 to 70 or preferably 55 to 60 or 65, and especially about 65, weight percent of a butene -1 polymer, (ii) from 5 to 25, preferably to 15 or 20, and especially about 10, weight percent of an ethylenic polymer, and (iii) from \to 45, preferably 25 to and especially about 25, weight percent of a propylene polymer, the percentages being based on the combined weight of (ii) and (iii).
The invention also provides a packaging film or sheet which is capable of forming a peel seal and is of a blend of the invention. The invention further provides a laminar structure comprising a polypropylene substrate to which is bonded, as by coextrusion or extrusion lamination, a coating layer of the blend or a packaging film or sheet in accordance with the invention.
Applicants have found that a wrappable film may be made which is capable of forming peel seals and comprises a mixture containing from about 5 percent by weight to about Spercent by weight of an ethylenic homopolymer or copolymer, from about 50 percent by weight to about 70 percent by weight of a butene-1 homopolymer or copolymer, and from about percent by weight to about 45 percent by weight propylene homopolymer or copolymer.
SA preferred blend in accordance with the invention comprises 55 to 60 or 65 percent by weight of 10 to percent by weight of (ii) and from 25 to 45 percent by weight of (iii). The most preferred blend comprises about j 20 percent by weight of about 10 percent by weight of (ii) and about 25 percent by weight of (iii).
The butene-1 polymer can be a homopolymer or a copolymer of butene-1 with a copolymerisable comonomer such as another olefin, for example ethylene, propylene and alphaolefins of 5 to 8 carbon atoms. The copolymers will usually contain a major molar proportion of units derived from butene-1.
S-6- The ethylenic polymer (ii) may be a homopolymer or copolymer and suitable examples include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA) ethylene- I l l b..1 t r r C
O
r (I tC i, TI CL Ay a cLy L copo yJU.1erIL e y J.IL-Uene- u y acLLY L C copolymer (EBA) and high density polyethylene (HDPE) and most preferably is low density polyethylene or ethylene-vinyl acetate copolymer. The copolymers will usually contain a major molar proportion of units derived from ethylene.
The propylene polymer (iii) can be a homopolymer or copolymer of propylene with a copolymerisable monomer.
Propylene copolymers will usually contain a major molar proportion of units derived from propylene. The propylene polymer (iii) improves the processability of the blend and its retortability (resistance to the temperature of the retort).
The polymer blends of the invention may be formed into an oriented (preferably biaxially oriented) or unoriented film or sheet by casting or film blowing. After fabrication the film or sheet can be heat sealed by sealing jaws at a preset temperature, pressure and dwell. The seal strength is tested by an Instron tensile tester at 25.4 cm/min (10″/min) crosshead speed. Maximum strength on a 2.54 cm (one inch) width strip was designated as peel seal strength.
S-7- These manufacturing techniques apply to film, but the blends can be used to form sheeting. Film refers to shaped plastics that are comparatively thin and have a maximum thickness of 0.025mm (0.01 inch). Sheeting refers to shaped plastics having a thickness greater than 0.025mm (0.01 inch).
The present invention also provides a laminar structure which comprises a polypropylene substrate to which is bonded a coating layer of the blend of the invention or a film or sheet of the blend. The peel seal coat, which consists of the blend of the invention, can be coated or laminated onto the substrate. Alternatively the laminar structure can be made by making two separate films that are then laminated. The individual films can be made by, for example, film blowing (melt extrusion with a circular die) or the casting method (a flat die-melt extrusion process).
Melt extrusion with a flat die (casting) may be accomplished for thermoplastic polymers by using a flat die or slot die. The extrusion process starts with a polymer in a form that can be fed continuously into an extruder by means of a screw or pneumatic tube. Sometimes the polymers are combined with materials such as plasticizers, lubricants, stabilizers and colourants by means of, for example, Banbury mixers. The resulting mix is extruded through rod shaped dies and chipped into pellets. Pelletized polymer is fed into a screw conveyer into the end of a screw-type extruder 111 i ~~rl -a=aaxr ~niuarsaun L rapr*r~i -8and is heated and made into viscous fluid in a cylinder by means of a revolving, helical screw. The sheet leaving the die is quenched on a temperature-controlled chill roll.
Finished films may be subject to a two-way stretching using continuous tenter-frame operations in biaxial orientation.
tt’ o. EXAMPLE Polybutylene PB8240 («DURAFLEX» Registered Trade Mark) having a melt index of about 2.0 dg/min (ASTM method D-1238 condition and a density of about 0.901 g/cm 3 was dry blended in a tumbler mixer with 12 w% of an ethylenevinyl S.»o acetate copolymer (EVA) having a 15 weight percent vinyl
